U.S. patent application number 12/336893 was filed with the patent office on 2010-06-17 for method and apparatus for performing remote calibration verification.
Invention is credited to Anton Hilger, Julia Hoff, Michael L. Kliewer, Gerhard Youssefi.
Application Number | 20100153047 12/336893 |
Document ID | / |
Family ID | 41719007 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100153047 |
Kind Code |
A1 |
Youssefi; Gerhard ; et
al. |
June 17, 2010 |
Method and Apparatus for Performing Remote Calibration
Verification
Abstract
A method and apparatus for remotely verifying the calibration
status of a diagnostic instrument, for example, following remote
installation of a software upgrade on the instrument. In one
example, a method of verifying the calibration status of the
instrument, includes retrieving stored raw calibration test data
generated during a previously-performed calibration of the
instrument, processing the raw calibration test data to generate a
diagnostic reading, comparing the diagnostic reading to a known
nominal reading, and based on the comparison, generating an output
indicative of the calibration status of the instrument. In one
example, the method is performed without contemporaneously
measuring a calibration object with the instrument and therefore,
without activating the measurement head or measurement optics of
the instrument.
Inventors: |
Youssefi; Gerhard;
(Landshut, DE) ; Hoff; Julia; (Munich, DE)
; Hilger; Anton; (Munich, DE) ; Kliewer; Michael
L.; (Fairport, NY) |
Correspondence
Address: |
Bausch & Lomb Incorporated
One Bausch & Lomb Place
Rochester
NY
14604-2701
US
|
Family ID: |
41719007 |
Appl. No.: |
12/336893 |
Filed: |
December 17, 2008 |
Current U.S.
Class: |
702/85 |
Current CPC
Class: |
G16H 40/40 20180101;
A61B 3/1015 20130101; A61B 2560/0271 20130101; A61B 3/135 20130101;
A61B 2560/0223 20130101 |
Class at
Publication: |
702/85 |
International
Class: |
G01D 18/00 20060101
G01D018/00 |
Claims
1. A method of remotely updating and verifying a calibration status
of an instrument that comprises a measurement portion and a
computer system coupled to the measurement portion, the method
comprising acts of: providing a software update to the instrument
from a remote location via a communications link; without
activating the measurement portion of the instrument, performing a
calibration check procedure at the instrument; and providing a
calibration status indicator that identifies the calibration status
of the instrument following the calibration check procedure.
2. The method as claimed in claim 1, wherein performing the
calibration check procedure includes: retrieving stored raw
calibration test data; processing the raw calibration test data to
generate a diagnostic reading; comparing the diagnostic reading to
a known correct nominal reading; and based on the comparison,
generating the calibration status indicator.
3. The method as claimed in claim 2, wherein performing the
calibration check procedure further comprises retrieving stored
calibration parameters; and wherein processing the raw calibration
test data is performed using the calibration parameters.
4. The method as claimed in claim 3, wherein generating the
calibration status indicator includes generating the calibration
status indicator that indicates that the calibration status of the
instrument is non-operational.
5. The method as claimed in claim 4, wherein generating the
calibration status indicator includes generating data that
identifies a corrupted calibration parameter.
6. The method as claimed in claim 2, wherein generating the
calibration status indicator includes generating a calibration
status indicator that indicates that the calibration status of the
instrument is operational.
7. The method as claimed in claim 2, wherein retrieving the stored
raw calibration test data includes retrieving a stored digital
image.
8. The method as claimed in claim 1, wherein providing the
calibration status indicator includes providing the calibration
status indicator from the instrument via the communications
link.
9. A method of verifying a calibration status of an instrument, the
method comprising acts of: retrieving stored raw calibration test
data; processing the raw calibration test data to generate a
diagnostic reading; comparing the diagnostic reading to a known
nominal reading; and based on the comparison, generating an output
indicative of the calibration status of the instrument; wherein the
verifying of the calibration status of the instrument is performed
without measuring a calibration object with the instrument.
10. The method as claimed in claim 9, wherein retrieving the stored
raw calibration test data includes retrieving a stored digital
image.
11. The method as claimed in claim 10, wherein processing the raw
calibration test data includes processing the raw calibration test
data using calibration parameters specific to the instrument.
12. The method as claimed in claim 11, wherein generating the
output indicative of the calibration status of the instrument
includes generating an output that identifies a corrupted
calibration parameter.
13. The method as claimed in claim 9, wherein generating the output
indicative of the calibration status of the instrument includes
generating an output that indicates instrument maintenance is
required.
14. The method as claimed in claim 9, wherein generating the output
indicative of the calibration status of the instrument includes
generating an output that indicates that the instrument is properly
calibrated.
15. A diagnostic system comprising: a measurement head; a storage
device coupled to the measurement head that stores raw calibration
test data generated by the measurement head; and a processor
coupled to the storage device and configured to retrieve the stored
raw calibration test data from the storage device without
activating the measurement head, to process the raw calibration
test data to generate a diagnostic reading, to compare the
diagnostic reading to a known nominal reading, and based on the
comparison, to generate an output indicative of a calibration
status of the diagnostic system.
16. The diagnostic system as claimed in claim 15, further
comprising a communications port coupled to a communications link
and to the processor; and wherein the processor is further
configured to transmit the output to a remote location via the
communications link.
17. The diagnostic system as claimed in claim 16, wherein the
processor is further configured to receive a software upgrade via
the communications link and to initiate a calibration check
procedure following installation of the software upgrade.
18. The diagnostic system as claimed in claim 15, wherein the
diagnostic system comprises at least one of a pupilometer, a
wavefront sensor, a placido device and a slit scan device.
19. The diagnostic system as claimed in claim 15, wherein the
storage device stores calibration parameters specific to the
diagnostic system; and wherein the processor is further configured
to retrieve at least one calibration parameter from the storage
device and to process the raw calibration test data using the at
least one calibration parameter to generate the diagnostic
reading.
20. The diagnostic system as claimed in claim 19, wherein the
output indicates that the calibration status of the diagnostic
system is invalid, and contains information indentifying at least
one corrupted calibration parameter.
21. The diagnostic system as claimed in claim 15, wherein the
stored raw calibration test data includes a digital image of a
calibration object.
Description
BACKGROUND
[0001] 1. Field of Invention
[0002] The present invention relates generally to servicing of
diagnostic systems and, more particularly, to verifying the
calibration status of a diagnostic system.
[0003] 2. Discussion of Related Art
[0004] For current existing diagnostic systems such as, for
example, optical diagnostic systems such as wavefront sensors or
corneal topography systems, calibration objects are used to perform
and test the hardware and software calibration of the diagnostic
system. These calibration objects are standardized devices having
accurately known characteristics. In general the calibration
procedure requires a trained operator who mounts and aligns the
calibration objects in or on the diagnostic system being
calibrated.
[0005] Referring to FIG. 1, there is illustrated a flow diagram of
a calibration procedure for a diagnostic system. First, in step
100, a calibration object is mounted and aligned on or in front of
the measurement head of the diagnostic system. After correct
alignment of the calibration object, a measurement of the
calibration object is performed (step 110). This step 110 is
referred to as an acquisition since data is acquired from the
measurement. In step 120, the collected data are processed to
create a diagnostic reading. This diagnostic reading is then
compared with expected results based on the known characteristics
of the calibration object (step 130). Based on the result of this
comparison, the operator is able determine either than the
calibration was successful (step 140) or that the calibration
failed, indicating a problem with either the calibration object or
the diagnostic system (step 150).
SUMMARY OF INVENTION
[0006] Aspects and embodiments are directed to methods and
apparatus to facilitate remote servicing of diagnostic devices,
particularly, to remotely verify the software calibration of a
diagnostic device following a software upgrade or other remote
service operation. By providing the ability to remotely (i.e., from
a location other than the location of the diagnostic device) verify
the calibration status, the usefulness and efficiency of remote
software service of diagnostic systems may be enhanced.
[0007] One embodiment is directed to a method of remotely updating
and verifying a calibration status of an instrument that comprises
a measurement portion and a computer system coupled to the
measurement portion. In one example, the instrument is a diagnostic
system. The method comprises acts of providing a software update to
the instrument from a remote location via a communications link,
without activating the measurement portion of the instrument,
performing a calibration check procedure at the instrument, and
providing a calibration status indicator that identifies the
calibration status of the instrument following the calibration
check procedure. In one example, performing the calibration check
procedure is done without contemporaneously activating the
measurement portion of the instrument. In another example,
performing the calibration check procedure does not include
contemporaneously measuring a calibration object with the
instrument.
[0008] According to one example, performing the calibration check
procedure includes retrieving stored calibration test data,
processing the calibration test data to generate a diagnostic
reading, comparing the diagnostic reading to a known correct
nominal reading, and based on the comparison, generating the
calibration status indicator. Performing the calibration check
procedure may further comprise retrieving stored calibration
parameters, wherein processing the calibration test data is
performed using the calibration parameters. Retrieving the stored
calibration test data includes retrieving a stored digital image.
According to another example, performing the calibration check
procedure includes retrieving stored raw calibration test data,
processing the raw calibration test data to generate a diagnostic
reading, comparing the diagnostic reading to a known correct
nominal reading, and based on the comparison, generating the
calibration status indicator. Retrieving the stored raw calibration
test data may include retrieving a stored digital image. Performing
the calibration check procedure may further comprise retrieving
stored calibration parameters, wherein processing the raw
calibration test data is performed using the calibration
parameters. In one example, generating the calibration status
indicator includes generating the calibration status indicator that
indicates that the calibration status of the instrument is
non-operational. Generating the calibration status indicator may
include generating data that identifies one or more corrupted
calibration parameters. Generating the calibration status indicator
may include generating a calibration status indicator that
indicates that the calibration status of the instrument is
operational. In one example, providing the calibration status
indicator includes providing the calibration status indicator from
the instrument via the communications link. In another example,
providing the calibration status indicator includes providing the
calibration status indicator from the instrument to a remote user
interface via the communications link.
[0009] Another embodiment is directed to a method of verifying a
calibration status of an instrument comprising a processor, the
method comprising acts of initiating a calibration check procedure
on the processor, retrieving stored raw calibration test data
obtained during a previously-performed calibration procedure on the
instrument, processing the raw calibration test data with the
processor to generate a diagnostic reading, and based on the
diagnostic reading, generating a calibration status indicator that
indicates whether the calibration check procedure passed or
failed.
[0010] In one example of the method, generating the calibration
status indicator includes an act of comparing the diagnostic
reading to a known nominal reading and generating the calibration
status indicator based on a result of the comparing act. In another
example, processing the raw calibration test data includes
processing the raw calibration test data using calibration
parameters specific to the instrument. In another example,
retrieving the stored raw calibration test data includes retrieving
a digital image of a calibration test object taken by the
instrument during the previously-performed calibration procedure.
The method may further comprise an act of providing the calibration
status indicator to a remote user interface via a communication
link between the instrument and the remote user interface. In one
example, verifying of the calibration status of the instrument is
performed without contemporaneously measuring a calibration object
with the instrument.
[0011] According to another embodiment, a method of verifying a
calibration status of an instrument comprising acts of retrieving
stored calibration test data, processing the calibration test data
to generate a diagnostic reading, comparing the diagnostic reading
to a known nominal reading, and based on the comparison, generating
an output indicative of the calibration status of the instrument,
wherein the verifying of the calibration status of the instrument
is performed without measuring a calibration object with the
instrument. In one example, retrieving the stored calibration test
data and processing the calibration test data to generate the
diagnostic reading comprises retrieving stored raw calibration test
data, and processing the raw calibration test data to generate the
diagnostic reading. In another example, verifying of the
calibration status of the instrument is performed without
contemporaneously measuring a calibration object with the
instrument. Retrieving the stored calibration test data may include
retrieving a stored digital image. Processing the calibration test
data may include processing the calibration test data using
calibration parameters specific to the instrument. In one example,
processing the raw calibration test data includes processing the
raw calibration test data using calibration parameters specific to
the instrument. Generating the output indicative of the calibration
status of the instrument may include generating an output that
identifies a corrupted calibration parameter. In another example,
generating the output indicative of the calibration status of the
instrument includes generating an output that indicates instrument
maintenance is required. In another example, generating the output
indicative of the calibration status of the instrument includes
generating an output that indicates that the instrument is properly
calibrated.
[0012] According to another embodiment, a diagnostic system
comprises a measurement portion, a computer system coupled to the
measurement portion, and a communications link coupled to the
computer system, wherein the computer system comprises a processor
configured to receive a software update from a remote location via
the communications link, to perform a calibration check procedure
of the diagnostic system without activating the measurement
portion, and to provide a calibration status indicator that
identifies the calibration status of the diagnostic system
following the calibration check procedure. In one example, the
processor is configured to verify of the calibration status of the
diagnostic system without contemporaneous measurement of a
calibration object with the measurement portion. In one example,
the processor is further configured to provide the calibration
status indicator to a remote user interface via the communications
link. In another example, the computer system further comprises a
storage device, and the processor is configured to perform the
calibration check procedure by retrieving stored raw calibration
test data from the storage device, processing the raw calibration
test data to generate a diagnostic reading, comparing the
diagnostic reading to a known nominal reading, and based on the
comparison, generating the calibration status indicator.
[0013] According to another embodiment, a diagnostic system
comprises a measurement head, a storage device coupled to the
measurement head and which stores raw calibration test data
generated by the measurement head, and a processor coupled to the
storage device. The processor is configured to retrieve the stored
raw calibration test data from the storage device without
activating the measurement head, to process the raw calibration
test data to generate a diagnostic reading, to compare the
diagnostic reading to a known nominal reading, and based on the
comparison, to generate an output indicative of a calibration
status of the diagnostic system. Thus, the processor may be
configured to verify a calibration status of the diagnostic system
without requiring contemporaneous measurement of a calibration
object with the measurement head.
[0014] In one example, the diagnostic system further comprises a
communications port coupled to a communications link and to the
processor, wherein the processor is further configured to transmit
the output to a remote location via the communications link. In
another example, the processor is further configured to receive a
software upgrade via the communications link and to initiate a
calibration check procedure following installation of the software
upgrade. The diagnostic system may comprise, for example, at least
one of a pupilometer, a wavefront sensor, a placido device and a
slit scan device. In one example, the storage device stores
calibration parameters specific to the diagnostic system, and the
processor is further configured to retrieve at least one
calibration parameter from the storage device and to process the
raw calibration test data using the at least one calibration
parameter to generate the diagnostic reading. In one example, the
output indicates that the calibration status of the diagnostic
system is invalid, and contains information indentifying at least
one corrupted calibration parameter. In another example, the stored
raw calibration test data includes a stored digital image of a
calibration object. The digital image may be acquired during a
calibration measurement performed prior to the calibration check
procedure.
[0015] According to another embodiment, computer-readable media
having computer-readable signals stored thereon that define
instructions which, as a result of being executed by a computer or
processor, instruct the processor to perform a method for verifying
the calibration status of an instrument are provided. The
computer-readable media include separate computer-readable media
with signals stored thereon for performing each individual element
of the methods described above, and computer-readable media for
performing the method elements described above in combination.
[0016] Still other aspects, embodiments, and advantages of these
exemplary aspects and embodiments, are discussed in detail below.
Moreover, it is to be understood that both the foregoing
information and the following detailed description are merely
illustrative examples of various aspects and embodiments, and are
intended to provide an overview or framework for understanding the
nature and character of the claimed aspects and embodiments. Any
embodiment disclosed herein may be combined with any other
embodiment in any manner consistent with the objects, aims, and
needs disclosed herein, and references to "an embodiment," "some
embodiments," "an alternate embodiment," "various embodiments,"
"one embodiment" or the like are not necessarily mutually exclusive
and are intended to indicate that a particular feature, structure,
or characteristic described in connection with the embodiment may
be included in at least one embodiment. The appearances of such
terms herein are not necessarily all referring to the same
embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Various aspects of at least one embodiment are discussed
below with reference to the accompanying figures, which are not
intended to be drawn to scale. The figures are included to provide
illustration and a further understanding of the various aspects and
embodiments, and are incorporated in and constitute a part of this
specification, but are not intended as a definition of the limits
of the invention. Where technical features in the figures, detailed
description or any claim are followed by references signs, the
reference signs have been included for the sole purpose of
increasing the intelligibility of the figures, detailed
description, and/or claims. Accordingly, neither the reference
signs nor their absence are intended to have any limiting effect on
the scope of any claim elements. In the figures, each identical or
nearly identical component that is illustrated in various figures
is represented by a like numeral. For purposes of clarity, not
every component may be labeled in every figure. In the figures:
[0018] FIG. 1 is a flow diagram of a conventional calibration
procedure;
[0019] FIG. 2 is a block diagram of one example of a diagnostic
system according to aspects of the invention;
[0020] FIG. 3 is a flow diagram of one example of a calibration or
calibration verification procedure, according to aspects of the
invention;
[0021] FIG. 4 is a flow diagram of one example of a remote
calibration verification procedure according to aspects of the
invention;
[0022] FIG. 5A is an example of a raw image of a pupil having a
defined aperture size of 5 mm;
[0023] FIG. 5B is an example of a processed image corresponding to
the raw image of FIG. 5A;
[0024] FIG. 6 is an example of a raw image of a calibration test
tool used to calibrate a wavefront sensor;
[0025] FIG. 7 is an illustration of one example of a wavefront
sensor lenslet array, according to aspects of the invention;
[0026] FIG. 8 is an example of a processed image corresponding to
the raw image of FIG. 6;
[0027] FIG. 9 is an example of a reference placido image;
[0028] FIG. 10 is a portion of a table illustrating exemplary
stored raw calibration test data corresponding to the placido image
of FIG. 9;
[0029] FIG. 11 is an example of a reference placido image used for
gain analysis of a placido device;
[0030] FIG. 12A is an example of a slit image of a reference sphere
with a defined radius; and
[0031] FIG. 12B is an example of an anterior elevation map of the
reference sphere.
DETAILED DESCRIPTION
[0032] Diagnostic systems generally include both hardware and
software portion. As illustrated in FIG. 3, the hardware of the
diagnostic system 200 includes a measurement head 210 that performs
measurements on test objects or calibration objects mounted on the
system, and a computer or processor 220. The computer 220 may be
implemented in a variety of ways, including, but not limited to, a
general purpose computer coupled to the measurement head 210, and
an integrated specialized computer. The computer 220 is programmed
with software that may perform or control various aspects and
functions of the diagnostic system, including, for example,
processing software to analyze the data acquired during such a
measurement and to generate the diagnostic reading. This software
may be periodically updated as part of the maintenance of the
diagnostic system. According to one embodiment, the diagnostic
system 200 is coupled to user interface at a remote location 230
via a communications link 240 to allow remote upgrades or updates
of the software to be performed via the communications link 240.
Thus, the computer 220 may include or be coupled to a
communications port 250. Examples of the communications link 240
include, but are not limited to, a wireless link, a wired link, a
fiber optic link, an Internet connection, a network connection,
etc. Similarly, the communications port 250 may be implemented
using standard systems.
[0033] As discussed above, typical calibration procedures for such
diagnostic systems include the mounting of calibration objects on
the diagnostic system and comparing the data from a measurement of
the calibration object with the nominal values. During the
calibration procedure, the unique hardware configuration of the
diagnostic system is included in the calculation of a measurement
analysis. If the calculated values, or diagnostic reading, obtained
from the measurement analysis are within a certain acceptance
range, then the diagnostic system is considered to be appropriately
calibrated, while any deviation from the acceptance range indicates
that the calibration status is no longer valid. The acceptance
range may be defined by ranges of accepted values for each of a
variety of calibration parameters. These calibration parameters
depend on the diagnostic system and may include, for example,
parameters such as the pixel size of the camera, the focal length
of the camera, the distance between mirrors, etc., as known to
those skilled in the art.
[0034] Since the calibration parameters are stored in the software
of the diagnostic system, it is possible that when a software
upgrade is installed, the calibration parameters may be corrupted.
Accordingly, when the software is updated, it is important to
verify the calibration status of the diagnostic device. As
discussed above, diagnostic systems can be communicatively coupled
to remote locations, such that remote software updates can be
performed. However, as also discussed above, conventional
calibration procedures generally require a trained operator to
mount and align the calibration object on the diagnostic system.
Therefore, even though the software update can be installed
remotely, complete software servicing of the diagnostic system
requires an on-site operator to verify the calibration.
[0035] According to one embodiment, by providing a method and
apparatus to remotely verify the calibration status of a diagnostic
system, the base for a remote software service is opened. As
discussed further below, aspects and embodiments avoid the need for
having an operator at the diagnostic system to check the
calibration status locally whenever a software upgrade is remotely
installed. In addition, embodiments of the methods and apparatus
discussed herein may be used to perform calibration status checks
at any time, for example, on a regular basis to detect unintended
changes in the diagnostic system, or after events, such as a power
failure, or at any other time when verification of the calibration
status of the diagnostic system is desired.
[0036] It is to be appreciated that embodiments of the methods and
apparatus discussed herein are not limited in application to the
details of construction and the arrangement of components set forth
in the following description or illustrated in the accompanying
figures. The methods and apparatus are capable of implementation in
other embodiments and of being practiced or of being carried out in
various ways. Examples of specific implementations are provided
herein for illustrative purposes only and are not intended to be
limiting. In particular, acts, elements and features discussed in
connection with any one or more embodiments are not intended to be
excluded from a similar role in any other embodiments.
[0037] Also, the phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. Any
references to embodiments or elements or acts of the systems and
methods herein referred to in the singular may also embrace
embodiments including a plurality of these elements, and any
references in plural to any embodiment or element or act herein may
also embrace embodiments including only a single element.
References in the singular or plural form are not intended to limit
the presently disclosed systems or methods, their components, acts,
or elements. The use herein of "including," "comprising," "having,"
"containing," "involving," and variations thereof is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. References to "or" may be construed as
inclusive so that any terms described using "or" may indicate any
of a single, more than one, and all of the described terms. Any
references to front and back, left and right, top and bottom, and
upper and lower are intended for convenience of description, not to
limit the present systems and methods or their components to any
one positional or spatial orientation.
[0038] Referring to FIG. 3, there is illustrated a flow diagram of
one example of a calibration or calibration verification procedure
similar to the calibration procedure discussed above with reference
to FIG. 1. According to one embodiment, when the measurement of the
calibration object is performed (step 110), raw digital data is
acquired. Step 300 includes storing this acquired raw data,
referred to as raw calibration test data, in a storage device or
memory device 260 forming part of or coupled to the computer 220 of
the diagnostic system 200 (see FIG. 2). In one example, in which
the diagnostic system is an optical system configured to measure
the human eye, the calibration objects for each individual
diagnostic system are designed to model the applicable
characteristics of a real eye. Accordingly, the typical data
collected during an acquisition is not significantly different from
data originating from a real eye. In one example, the raw data
acquired during step 110 are images taken by cameras (included in
the measurement head 210) which operate either in the visible or
the infrared range of the spectrum. Thus, the raw data may include
color images or greyscale images that may be stored as digital
data. Similarly, in other examples in which the diagnostic systems
analyze things other than the eye, (e.g., spectrum analyzers,
spectrometers, etc.), the acquired raw data may be images or
numeric data that can be stored as digital data. Accordingly,
although the following discussion may refer to examples of optical
diagnostic systems, it is to be appreciated that the invention is
not so limited and may be applied to any type of diagnostic system
in which digital data is acquired during the calibration
procedure.
[0039] Still referring to FIG. 3, in step 310 the processing
software processes the acquired images and the outcome of the
analysis is a set of values which are used to either calibrate or
determine the calibration status of the system. As discussed above,
the measurement of the calibration object (step 110) includes the
unique hardware configuration of the diagnostic system.
Accordingly, steps 100 and 110 are "hardware related" in that they
rely on and incorporate aspects of the measurement head 210. If no
changes are made to the hardware, for example, only a software
update is performed, then the hardware-related parts of the
calibration procedure (steps 100 and 110) should be stable within
the established maintenance interval for the diagnostic system.
[0040] Accordingly, in one embodiment, a method of verifying the
calibration status of a diagnostic system is independent of the
hardware-related portions of a conventional calibration procedure
and therefore, may be performed remotely. According to one
embodiment, the method uses raw calibration test data from a
previously performed calibration procedure that was stored in
storage device 260 during step 300 in conjunction with the stored
calibration parameters to verify whether the calibration status of
the diagnostic system is valid, or whether an event (such as
corruption of one or more calibration parameters during a software
upgrade) has invalidated the calibration status of the system.
[0041] Referring to FIG. 4, there is illustrated a flow diagram of
one example of a method for verifying the calibration status of a
diagnostic system. In step 400, the diagnostic system enters a
calibration check mode to perform the calibration check procedure.
The calibration check mode may be initiated, for example, by a
command issued to the computer 220 from the remote user interface
230. The command to initiate the calibration check procedure may be
issued responsive to a condition or event such as, but not limited
to, following a software upgrade installed on the diagnostic
system, a power failure at the location of the diagnostic system, a
crash of the computer 220, or as part of a routine maintenance
event. In another example, the calibration check mode may be
entered automatically based on policies, such as maintenance
schedule, stored on the computer 220 or automatically transmitted
to the computer 220 via the communications link 240.
[0042] Once the calibration check procedure is initiated, the
processing software uploads the stored raw data set and the stored
calibration parameters into the processing stream (step 410). This
makes the mounting of a calibration object obsolete. Accordingly,
in one example, steps 100 and 110 of a conventional calibration
procedure are replaced with steps 400 and 410 of the calibration
check procedure. The stored raw data set is processed based on the
stored calibration parameters to generate a diagnostic reading
(step 420). If the calibration parameters are correct, assuming no
other errors in the processing software, the diagnostic reading
will correspond to a known set of outcomes. In this case, comparing
the calculated diagnostic reading with known correct nominal values
(step 430) will yield an expected result, and the processing
software generates a calibration status indicator indicating that
the calibration check passed successfully (step 440).
Alternatively, if any of the calibration parameters are corrupted,
or another error has occurred in the processing software, the
result of step 430 will indicate that the diagnostic reading is
outside of the defined acceptance range. In this case, the
processing software generates a calibration status indicator that
indicates that the calibration check has failed, i.e., the
calibration status of the diagnostic system is invalid or
non-operational, and accordingly, service of the diagnostic system
may be required (step 450).
[0043] According to one embodiment, the computer 220 sends the
calibration status indicator to the remote user interface 230 via
the communications link 240. Thus, the calibration check procedure
may be initiated remotely and the result of the procedure may be
viewed remotely. Furthermore, the calibration check procedure does
not require a calibration object to be mounted on the diagnostic
system and does not require the measurement head of the instrument
to be activated. Therefore, the calibration check procedure may be
performed without an on-site operator present, and only the
portions of the computer 220 required to access the storage device,
perform the data processing, and transmit the calibration status
indicator to the remote location need be active. Thus, embodiments
of the method and apparatus allow an operator to perform a remote
calibration test of the software components of the diagnostic
device. This may greatly enhance the value of performing remote
software upgrades to the diagnostic device since the calibration
verification can also be done remotely, and may provide a solid
regulatory base for remotely upgrading the software of diagnostic
devices. Furthermore, the ability to remotely verify the
calibration status of the instrument following a software upgrade
or other event may greatly reduce the cost of these activities and
of the maintenance of the instrument since the need for a local,
trained operator to perform the calibration is avoided.
[0044] In addition, when the calibration check procedure fails, the
calibration status indicator may contain information that allows a
remote operator to diagnose what type of error has occurred, or
which calibration parameter has been corrupted. This may allow the
remote operator to initiate appropriate maintenance and direct an
appropriate technician to service the instrument more quickly and
more cost effectively. In particular, certain calibration
parameters are directly related to recognizable features in the
processed images or data streams. Accordingly, a change in one of
these recognizable features may indicate to the operator which
calibration parameter has been affected. For example, in an optical
imaging system, the distance between the camera and the calibration
object results in defocusing or magnetization of the entire image.
Accordingly, if the processed image resulting from step 420 is
either out of focus or enlarged/reduced in size compared to the
expected result, this may indicate to the operator that the
distance calibration parameter is corrupted.
[0045] In one example, the computer 220 may transmit the processed
data to the remote user interface to be analyzed by the remote
operator. Thus, the calibration status indicator may include the
processed data. In another example, the processing software may
identify candidate corrupted calibration parameters based on the
result of the comparison step 403, and the calibration status
indicator may include information identifying the candidate
corrupted parameters. As will be recognized by those skilled in the
art given the benefit of this disclosure, there are numerous
variations on the information and data that may included in the
calibration status indicator, including simply an indication that
the calibration status is either valid/operational or
invalid/non-operational. Furthermore, in one example, the
calibration status indicator, optionally including the processed
image, may be displayed locally by the computer 220 as well as, or
instead of, being transmitted to the remote location. Similarly,
the computer 220 may store the calibration status indicator for
later access by a local operator.
[0046] In one embodiment, the raw data sets and calibration
parameters are renewed and updated with each service action
performed on-site by service personnel. For example, the raw data
sets and/or calibration parameters may be updated when changes to
the system hardware are made or during regular maintenance of the
system. The raw data sets may also be updated when an operator
performs a manual calibration of the diagnostic system, whether
part of routine maintenance or not. Updating the stored raw data
sets and calibration parameters may ensure that the remote software
calibration checks are valid and accurate because current data is
used. Furthermore, the use of digital data, rather than a physical
calibration object, to perform the calibration check procedure may
offer several advantages. For example, the characteristics of
calibration objects may vary with changing environmental
conditions, such as temperature or humidity; whereas stored digital
data remains constant over time. In addition, various methods exist
for verifying that digital data has in fact remained the same over
time, such as, for example, checksum or other procedures.
Accordingly, a more accurate calibration check result may be
obtained using the stored digital data rather than a physical
calibration object.
[0047] Embodiments of the calibration check procedure and method
may be used for a variety of different measurement concepts and
applied to many different diagnostic systems. The following
examples serve to illustrate some of the novel features, aspect and
examples of the technology disclosed herein and should not be
construed as limiting the scope of the appended claims.
EXAMPLE 1
[0048] In one example, the calibration check procedure and method
can be applied to a pupilometer. The reference of the pupilometer
is set via a pupil image of a calibration object with a defined
aperture. Accordingly, after the alignment of the appropriate
calibration object in front of the pupilometer, the image
illustrated in FIG. 5A is acquired using the pupil camera. FIG. 5
is an image of the pupil size (aperture size) for a calibration
object with a defined aperture size of 5 mm. This image is the raw
data set that is stored as digital data in step 300. As the size of
the physical aperture of the calibration object is known, the
analysis of the image needs to provide the specified size. Assuming
that the calibration object is positioned correctly, any deviation
from this predefined size indicates a problem, for example, wrong
configuration of a calibration parameter.
[0049] One example of a pupilometer calibration parameter is the
camera pixel to millimeter adjustment factor. Camera images are
typically analyzed in pixel coordinates, thus the first information
about the pupil diameter will be given in terms of the number of
pixels (N.sub.pix) inside the pupil. To determine the physical
pupil size in millimeters, the camera-specific pixel-to-mm
conversion factor (Pix2 mm) is utilized. This conversion factor is
an example of a system calibration parameter which is given for any
particular system and defined at the production of the system. Any
software changes to the system should not modify this parameter.
However, as discussed above, it is possible that this calibration
parameter may be overwritten by a wrong value during a software
upgrade. Corrupting this calibration parameter would lead to
incorrectly concluded pupil diameters.
[0050] Accordingly, in one example, a remote calibration check may
be used for verification of this calibration parameter which
defines the number of .mu.m per camera pixel. For a remote
calibration check of the pupilometer, the digital raw data set
corresponding to the pupil camera image of FIG. 5A is uploaded into
the processing stream (step 410). In the processing step 430, the
aperture size is calculated and, in the analysis step 440, the
calculated aperture size is compared to the predefined expected
value. For example, where the nominal pupil diameter O.sub.nom is
known, the calibration check procedure can be used to determine the
number of pixels, and by applying the Pix2 mm calibration
parameter, will calculate the actual pupil diameter, O.sub.act
using the equation:
O.sub.act=N.sub.pix.times.Pix2 mm (1)
A comparison between O.sub.act and O.sub.nom during step 420 may
lead to a conclusion about the status of the system calibration
parameter Pix2 mm. Thus, step 430 of generating the calibration
status indicator may include generating a status indicator that
indicates whether or not the Pix2 mm calibration parameter is
correct or not.
[0051] Additionally, if the calibration is correct, the processed
image will resemble that shown in FIG. 5B, which is an image of a
correctly adjusted pupil circle. As discussed above, following step
430, a calibration status indicator is generated, indicating either
that the calibration status of the pupilometer is operational (step
440) or non-operational (step 450), and is saved on the computer
220, transmitted to the remote user interface 230, and/or locally
displayed by the computer 220.
EXAMPLE 2
[0052] In another example, the calibration check procedure may be
applied to a wavefront sensor. A wavefront sensor, also referred to
as an aberrometer (which term will be used interchangeably herein),
is a device that measures a difference in the optical path of light
between a deformed wavefront and an ideal, or reference, wavefront.
The measurement, when properly processed, yields values for various
aberrations in the optical system that the light propagates
through, and which deform the wavefront. Wavefront sensors are used
in a variety of applications, including high-energy lasers,
astronomical imaging, and measuring the aberrations of the eye with
the goal of improving visual quality. One example of a wavefront
sensor is the Shack-Hartmann type wavefront sensing instrument that
can be used to measure, among other parameters, higher-order ocular
aberrations.
[0053] To calibrate the wavefront sensor, centroid images of test
tools are analyzed and the calibration values are saved in the
calibration data. An example of a raw image of a test tool used to
calibrate the wavefront sensor is given in FIG. 6. The raw images
are saved as digital raw data sets during step 300. The recognized
positions of the centroids in combination with the focal length of
the lenslet array (f) and the related pitch of the lenslet array
determine the outcome of such a Hartmann-Shack sensor. The lenslet
array parameters are examples of calibration parameters that could
be overwritten by wrong values during a software upgrade.
[0054] For example, referring to FIG. 7, there is illustrated a
diagram of one example of a wavefront sensor, showing the
relationship between values calculated during analysis of the
stored raw data and system calibration parameters. A wavefront
sensor such as discussed in this example measures the tilt of the
wavefront or in other words the angle (.alpha.) of the wavefront
propagating through the system. The tilt in the wavefront leads to
a spatial shift (.DELTA.x) of the focused bundle of light rays
which propagates through the lenslet array and generates the
centroid image. The tilt of the wavefront (.alpha.) or the tangent
of this angle (tan [.alpha.]) has a direct relation to the measured
displacement (.DELTA.x) and the focal length of the lenslet array
(f), as given by the following equation:
tan ( .alpha. ) = .DELTA. x f ( 2 ) ##EQU00001##
[0055] Accordingly, in one example, a remote calibration check of
the wavefront sensor can be used to verify the calibration
parameter that defines the focal length of the lenslet array (f).
In another example, the remote calibration check may also be used
to verify the calibration parameter that defines the camera pixel
to millimeter adjustment factor as the calculated displacement
value (.DELTA.x) is dependent on the pixel to millimeter adjustment
factor.
[0056] In one example, for a remote calibration check of the
wavefront sensor, in step 401, the raw Hartman-Shack images (FIG.
6) of calibration spheres are reloaded into the processing stream.
The processing software analyses the raw images and calculates the
diagnostic reading (step 420). In one example, the diagnostic
reading can include a tilt angle (.alpha..sub.act). Having a
nominal tilt angle .alpha..sub.nom given as the target value, any
deviation in the actual determined angle .alpha..sub.act will
indicate a deviation of either the system calibration parameter f
or the determined value .DELTA.x which, as discussed above, is
itself dependent on the camera calibration factor Pix2 mm. Thus, in
step 430, the processing software which checks the diagnostic
reading against defined acceptance criteria may check the
determined angle .alpha..sub.act against the nominal tilt angle
.alpha..sub.nom to determine whether or not the calibration status
of the wavefront sensor is valid. FIG. 8 is an example of a
processed image, obtained following step 420, corresponding to the
raw image illustrated in FIG. 6. As discussed above, following step
430, a calibration status indicator is generated, indicating either
that the calibration status of the wavefront sensor is operational
(step 440) or non-operational (step 450), and is saved on the
computer 220, transmitted to the remote user interface 230, and/or
locally displayed by the computer 220. In one example, in step 450,
the calibration status indicator may indicate an error in either
one of the calibration parameters f or Pix2 mm, as discussed
above.
EXAMPLE 3
[0057] In another example, the calibration check procedure may be
applied to a topographer, such as, for example, the Orbscan.TM.
device available from Bausch and Lomb, Inc. The Orbscan.TM.
instrument is an example for a diagnostic system which incorporates
two different modules in one system, namely a placido device and a
slit scan device. The calibration check procedure can be used to
remotely verify the calibration status of one or both of these
modules.
[0058] The placido device is calibrated using a reference sphere
having defined dimensions. During calibration, a reference placido
image, such as that illustrated in FIG. 9, of the defined reference
sphere. The ring positions of the reference sphere are evaluated
and stored during step 300. FIG. 10 illustrates an example of the
stored raw digital calibration test data corresponding to the
reference image of FIG. 9. Additionally the gain of the camera can
analyzed and checked with the acquired placido image. FIG. 11
illustrates an example of a reference placido image for gain
analysis.
[0059] To perform a remote calibration check of the placido device,
the raw calibration test data (FIG. 10) corresponding to the raw
placido images (FIG. 9) of the calibration sphere are loaded into
the processing steam (step 410). The processing software analyzes
the images (data) and calculates the related parameters to generate
the diagnostic reading (step 420). The diagnostic reading then
compared with defined acceptance criteria (step 430) to determine
whether or not the calibration status of the module is valid.
Similarly, to check the gain of the camera, the reference image
(FIG. 11) is analyzed and the resulting gain measurement is
compared with pre-defined ideal gain values.
[0060] To calibrate the slit scan device, multiple slit images
which are acquired during one acquisition are analyzed. The
detected edges of the slits are visually checked for disturbance.
If the slits show no inconsistencies, the elevation of the anterior
surface is analyzed and the results compared to an acceptance
window. An example of a raw slit image and a related elevation map
resulting from the processing of the raw image are shown in FIGS.
12A and 12B, respectively.
[0061] To perform a remote calibration check of the slit scan
device, the raw slit images of the calibration sphere (FIG. 12A)
are uploaded into the processing stream (step 410). The images are
analyzed and the related diagnostic reading calculated (step 420).
As discussed above, the diagnostic reading is compared to a known
correct nominal reading (step 430) and a calibration status
indicator is generated. In one example, the calibration status
indicator may combine the results from the calibration check of
both the placido device and the slit scan device to indicate
whether or not the calibration status of the topographer as a whole
is valid. Alternatively, the calibration status indicator may
include individual indications as to whether or not the calibration
statuses of the individual modules are valid.
[0062] The above examples illustrate how different instruments as
well as the various subsystems of a complex diagnostic system can
be remotely checked for appropriate software calibration. As will
be appreciated by those skilled in the art given the benefit of
this disclosure, embodiments of the calibration check procedure may
be applies to any kind of diagnostic system which is based on a
type of image acquisition technology. In addition, non-image data
streams may similarly be injected into the processing step of
embodiments of the calibration check method to replicate other
kinds of diagnostic data, such as, for example, an A-Scan generated
by a partial coherence interferometer used for the determination of
the eye length.
[0063] Having thus described several aspects of at least one
embodiment, it is to be appreciated various alterations,
modifications, and improvements will readily occur to those skilled
in the art. Such alterations, modifications, and improvements are
intended to be part of this disclosure and are intended to be
within the scope of the invention. Accordingly, the foregoing
description and drawings are by way of example only, and the scope
of the invention should be determined from proper construction of
the appended claims, and their equivalents.
* * * * *